seashells (mollusks) & beachcombing

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Seashells (mollusks) & beachcombing Maia McGuire, PhD Florida Sea Grant Extension Agent

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Seashells (mollusks) & beachcombing. Maia McGuire, PhD Florida Sea Grant Extension Agent. Mollusks. Includes Gastropods (snails), Bivalves (e.g. clams) and Cephalopods (e.g. octopus) Second largest invertebrate phylum (after arthropods). - PowerPoint PPT Presentation

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Page 1: Seashells (mollusks) & beachcombing

Seashells (mollusks) & beachcombing

Maia McGuire, PhDFlorida Sea Grant Extension Agent

Page 2: Seashells (mollusks) & beachcombing

Mollusks• Includes Gastropods (snails), Bivalves (e.g.

clams) and Cephalopods (e.g. octopus)• Second largest invertebrate phylum (after

arthropods)• Generally have a muscular

foot, a calcareous shell and a feeding organ called a radula

• Have gills, blood vascular system, stomach, heart, sensory organs (e.g. eyes)

Page 3: Seashells (mollusks) & beachcombing

Molluscan reproduction• Sexual reproduction• Most are single sex (gonochoric)• Fertilization is external• Larvae are often planktonic (most common

type is called a veliger)

Page 4: Seashells (mollusks) & beachcombing

Gastropods

• Snails and sea slugs• “Head foot”• Carnivores and herbivores• There are gastropods in salt water, fresh water

and on land, but all are restricted to that particular habitat. Land snails have lungs.

• Many have an operculum (“trap door”) to seal the entrance to their shell.

Page 5: Seashells (mollusks) & beachcombing

Gastropod adaptations

• Operculum (‘trap door”)– Used to help protect snail from predators– Used to help prevent snails from drying out

(especially for intertidal snails)– Different types of snails have different types of

opercula (range from thin and flimsy, to made of calcium carbonate)

Page 6: Seashells (mollusks) & beachcombing

Some snails are predators

• Remember that radula?• It becomes a drill or rasp that some snails use

to drill through the shells of other snails or bivalves (e.g. clams)

www.seaslugforum.net

Page 7: Seashells (mollusks) & beachcombing

Common gastropods

• Slipper shell• Moon snail/shark’s eye• Olive• Auger• Wentletrap• Baby’s ear• Whelks• Tulips

Page 8: Seashells (mollusks) & beachcombing

Gastropod egg cases

• Sand collar (moon snail)

• Whelk and tulip egg cases

www.jaxshells.org

Page 9: Seashells (mollusks) & beachcombing

Baby snails

• Often planktonic (carried by ocean currents)• Have a tiny shell, which becomes the tip of the

shell after the animal settles and grows.

Page 10: Seashells (mollusks) & beachcombing

Snail growth

• Snails add to their shell (at the opening/lip, and in thickness) as they grow.

• The mantle used calcium and bicarbonate ions from the water to create calcium carbonate.

• We cannot age a shell based on growth lines (unlike trees and corals)

Page 11: Seashells (mollusks) & beachcombing

Sea slugs• No external shell• Variety of defense mechanisms• Some are herbivores, others are carnivores

Page 12: Seashells (mollusks) & beachcombing

Bivalves• Have two, hinged shells• Examples include oysters, clams, mussels,

scallops• Many can live 20-30 years; some more than

100 years!• Most are filter-feeders• Many attach to hard surfaces; some have threads or cement

Page 13: Seashells (mollusks) & beachcombing

Bivalve shells

• Some bivalves have a periostracum (thin, often brown covering over the shell)—provides camouflage.

Page 14: Seashells (mollusks) & beachcombing

Common bivalves

• Ark clams

• Pen shells

• Coquina clams

• Jingles

• Cockles

• Scallops

Page 15: Seashells (mollusks) & beachcombing

Cephalopods

• Octopus, squid, nautilus, cuttlefish• Swim by producing a jet of water through a

funnel• Most have 2 tentacles with suction cup ends;

8 arms with suction cups• Horny, parrot-like beak; radula functions as a

tongue• Have pigment cells in skin

Page 16: Seashells (mollusks) & beachcombing

Cephalopod biology

• Many can squirt ink as a defense• Eyes and nervous system are well-developed• Carnivores• Poisonous saliva• Have gills, heart, brain• Gonochoric• Squid die after mating• Female octopus die after

brooding their eggs

Page 17: Seashells (mollusks) & beachcombing

• Paper nautilus

• Ram’s horn shell

www.manandmollusc.net

Cephalopods

www.seabean.comwww.seabean.com

Page 18: Seashells (mollusks) & beachcombing

Activities

• “I Have a Shell” (Monterey Bay Aquarium)• “CSI: Clamshell Investigation” (NJ Sea Grant)

Page 19: Seashells (mollusks) & beachcombing

Weird and Wonderful things…

• Mermaid’s purse

• Sand dollar

• Sea stars

Page 20: Seashells (mollusks) & beachcombing

Jellyfish• Portuguese man-o-war– Don’t touch!– Associated companions—”By-the-wind

sailor”, “blue buttons”, purple sea snail, man-o-war slug, man-o-war fish

www.enature.com

www.amonline.net.au

Page 21: Seashells (mollusks) & beachcombing

Cannonball jellyfish

www.jaxshells.org

Page 22: Seashells (mollusks) & beachcombing

Moon jellyfish

www.jaxshells.org

Page 23: Seashells (mollusks) & beachcombing

Sharks’ teeth

Page 24: Seashells (mollusks) & beachcombing

Sea beans

• www.seabean.com• Any of a number of seeds

that are adapted to germinate even after spending a period of time floating in water

• Mostly from tropical plants, many from vines

Page 25: Seashells (mollusks) & beachcombing
Page 26: Seashells (mollusks) & beachcombing

Activity

• Beach Treasures